EP3509773B1

EP3509773B1 - Method and apparatus for forming a beaded can end

Info

Publication number: EP3509773B1
Application number: EP18750047.5A
Authority: EP
Inventors: Stephen B. Turner; Shawn P. Finley
Original assignee: Alfons Haar Inc
Current assignee: Alfons Haar Inc
Priority date: 2017-11-29
Filing date: 2018-07-19
Publication date: 2020-01-29
Anticipated expiration: 2038-07-19
Also published as: ES2778696T3; JP6728533B2; DK3509773T3; CN110099760B; JP2020504009A; KR102177383B1; CO2019001506A2; AU2018308962B2; ECSP19010713A; KR20190083643A; HUE051743T2; US20190160517A1; CL2019000347A1; MX2019001916A; US10946432B2; WO2019108269A1; BR112019005786A2; CN110099760A; AU2018308962A1; EP3509773A1

Description

TECHNICAL FIELD

The present invention relates to manufacturing methods and to an apparatus for forming metallic can ends, according to the preambles of claims 1, 11 and 16 respectively, and more particularly to methods and to an apparatus for forming can ends with little or no stretching, and with minimal thinning of material during formation of the can end.

BACKGROUND ART

Metallic beverage can ends are designed to have one or more stiffening beads extending around the can end adjacent the circumference or periphery of the can end. These beads are typically defined by interconnected bead radii and bead valley radii alternating with one another in a radial direction of the can end. The beads are formed inward from a countersink radius, or chuckwall radius, and can be located outward from a central panel portion of the can end.
Beverage can bodies and can ends must be sufficiently strong to withstand high internal pressures and also external forces resulting from shipment and handling. Additionally, they must be manufactured from extremely thin and durable materials to reduce costs of manufacturing and weight of the finished products. These seemingly incompatible requirements of high strength and light weight can be accomplished by aggressively working the thin materials using interacting male and female tool combinations. Unfortunately, aggressive material working can lead to inconsistencies within a given contour or geometry of can ends due to excessive stretching or thinning of material from which the can ends are made. Such inconsistencies resulting during formation may diminish strength and alter other characteristics of the can ends.
EP1126939B1 , on which for example the preambles of claims 1, 11 and 16 are based, relates to methods and apparatus for forming a beaded can end. A can end is formed from sheet material in a single acting press by blanking a workpiece and holding the workpiece between a blanking punch and a draw pad. The periphery of the workpiece is worked between a knockout and a crown ring to contour a crown. A bead punch advances into the workpiece to form a shell extending from the crown. The bead punch bottoms out on a bead die and collapses to a predetermined position to form a plurality of beads adjacent the shell by flowing a portion of the shell to form the beads while shortening the shell to less than specifications for the can end. The bead punch returns to an uncollapsed position during upstroke of the press to extend the shell to be within specifications.
In the present application, techniques for controlling stretching and thinning in formed portions of can ends are illustrated in methods and apparatus for forming can ends from thin stock that exhibit required strength and possess improved consistency.

DISCLOSURE OF THE INVENTION

In accordance with an aspect of the invention, a method for forming a can end in a forming press with the steps of independent claim 1 is provided. The method comprises positioning a sheet of material between an upper punch assembly and a fixed base assembly in the forming press; cutting a can end blank from the sheet of material; clamping a peripheral portion of the can end blank; moving the upper punch assembly from a retracted position toward an extended position, and clamping a central portion of the can end blank between an upper panel punch and a lower panel punch to define a central panel section on the can end blank, wherein the central panel section is below an annular inner bead die located adjacent to the lower panel punch on the fixed base assembly; and extending the upper punch assembly subsequent to clamping the central portion of the can end blank to form an initial annular countersink radius next to the peripheral portion of the can end blank, with a substantially undeformed intermediate area extending between the initial annular countersink radius and the annular inner bead die.
The upper punch assembly may be extended to engage an annular first intermediate bead punch against the can end blank and a first intermediate bead valley radius may be initially formed in the intermediate area of the can end blank, and the depth of the countersink radius may be simultaneously increased.
The upper punch assembly may be further extended to engage an annular second intermediate bead punch against the can end blank and initially form a second intermediate bead valley radius in the intermediate area of the can end blank, wherein the depth of the first intermediate bead valley radius and the countersink radius may be simultaneously increased.
Forming the initial annular countersink radius may comprise engaging the can end blank with an outer bead punch on the upper punch assembly after an initial engagement of the upper panel punch against the can end blank.
Initial formation of the annular countersink radius may include upward displacement of the upper panel punch relative to the outer bead punch while the upper panel punch clamps the central panel section to the lower panel punch.
The peripheral portion of the can end blank may be clamped on a crown ring of the fixed base assembly, and the outer bead punch may cooperate with an inner wall of the crown ring to form a generally vertical outer wall of the countersink radius.
The upper punch assembly may include an annular outer bead punch, an annular middle bead punch, and an annular inner bead punch, and the fixed base assembly may include an annular outer bead die, an annular middle bead die, and the annular inner bead die, and wherein, subsequent to an initial engagement of the outer bead punch on the can end blank: the undeformed intermediate area of the can end blank may extend in engagement with the outer bead die, the middle bead die and the inner bead die; and the middle bead punch and the inner bead punch may be located spaced from the can end blank.
The middle bead punch may engage the can end blank prior to an engagement of the inner bead punch on the can end blank.
The outer bead punch and the inner bead punch may extend downward farther than the middle bead punch.
Movement of the upper punch assembly to its extended position may complete formation of the can end blank into a can end having a countersink radius, a middle bead valley radius, and an inner bead valley radius, wherein the central panel section may remain clamped between the upper panel punch and the lower panel punch during the entire formation of the beads.
In accordance with another aspect of the invention, a method for forming a can end in a forming press with the steps of independent claim 11 is provided. The method comprises positioning a sheet of material between an upper punch assembly and a fixed base assembly in the forming press; cutting a can end blank from the sheet of material; clamping a peripheral portion of the can end blank between a crown ring and a knockout ring; providing an upper punch assembly having a plurality annular bead punches and an upper panel punch supported for movement relative to the bead punches; providing a fixed base assembly having a plurality of annular bead dies for cooperating with the bead punches and a lower panel punch; moving the upper punch assembly from a retracted position toward an extended position. In addition, movement of the upper punch assembly comprises: engaging a central portion of the can end blank with the upper panel punch prior to engagement of the can end blank with the bead punches or the bead dies; and subsequently moving the upper punch assembly to clamp the central portion of the can end blank between the upper panel punch and the lower panel punch with the can end blank engaged with a single one of the bead punches and a single one of the bead dies.
The upper punch assembly may be extended subsequent to clamping the central portion of the can end such that the single one of the bead punches moves the can end blank down into engagement with one or more of the remaining bead dies.
Subsequent to the can end blank moving into engagement with the one or more of the remaining bead dies, further movement of the upper punch assembly may move the remaining bead punches into engagement with the can end blank.
The single one of the bead punches may comprise a radially outermost bead punch and the single one of the bead dies may comprise a radially innermost bead die.
A substantially undeformed intermediate area may extend between the outermost bead punch and the innermost bead die.
The lower panel punch may be immovably fixed relative to the bead dies.
In accordance with a further aspect of the invention, an apparatus according to the features of independent claim 16 is provided, the apparatus being for forming a can end from a sheet of material in a single acting press having a fixed base assembly and a movable upper punch assembly. The apparatus comprises a crown ring rigidly supported on the fixed base assembly and having an upper surface defining a contour for a crown of the can end. A knockout ring is carried by the upper punch assembly, the knockout ring being aligned with the crown ring for engaging a workpiece upon movement of the upper punch assembly toward the fixed base assembly to form a crown in a peripheral portion of the workpiece. A plurality of annular bead punches are supported on the upper punch assembly and an upper panel punch is fluidly supported on the upper punch assembly for movement relative to the bead punches. A plurality of annular bead dies and a lower panel punch are supported on the fixed base assembly for cooperating with the bead punches and the upper panel punch, respectively. Movement of the upper punch assembly from a retracted position toward an extended position engages the workpiece between the crown ring and the knockout ring, and positions the upper panel punch in engagement with the workpiece prior to engagement of the workpiece with the bead punches or the bead dies. Subsequent movement of the upper punch assembly clamps the workpiece between the upper panel punch and the lower panel punch with the workpiece engaged with a single one of the bead punches and a single one of the bead dies.
The upper panel punch may displace into the upper punch assembly during movement of the punch assembly toward the extended position subsequent to clamping the workpiece between the upper panel punch and the lower panel punch.
The plurality of bead punches on the upper punch assembly may be supported in fixed relation to each other and the upper panel punch may be movable relative to the plurality of bead punches.

BRIEF DESCRIPTION OF DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:

Fig. 1 is a schematic sectional view showing a forming press operable in accordance with aspects of the present description illustrating an upper punch assembly of the forming press in a lowered position at the initiation of a blank forming process for forming a can end;
Fig. 2 is an enlarged schematic sectional view of the forming press of Fig. 1 immediately following clamping of a workpiece between a draw punch and draw pad in preparation for a blanking operation;
Fig. 3 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating clamping engagement of a blank between a knockout ring and a crown ring;
Fig. 4 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 immediately following a clamping engagement of the blank between an upper panel punch and a lower panel punch;
Fig. 5 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating an initial step in formation of an outer bead for the can end;
Fig. 6 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating a further downward movement of the upper punch assembly positioning the blank adjacent to the upper bead dies;
Fig. 7 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating a further downward movement of the upper punch assembly to position the blank in engagement with an outer bead die for formation of the outer bead of the can end;
Fig. 8 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating a further downward movement of the upper punch assembly to form a middle bead of the can end;
Fig. 9 is an enlarged schematic sectional view showing portions of the forming press of Fig. 1 illustrating a further downward movement of the upper punch assembly to form an inner bead of the can end; and
Fig. 10 is a sectional view of an exemplary can end formed in accordance with aspects of the present description.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention as defined in the appended claims.
The present application discloses methods and apparatus for forming panels, shells, or can ends so that formed portions of the can ends have controlled thinning to substantially prevent warping, twisting and/or fractures that may occur if thinning is uncontrolled. In accordance with an aspect of the disclosed methods and apparatus, the formed portions of the can ends can be produced with no stretching, or negligible stretching, of the material during the forming process.
Reference is now made to Fig. 1 which illustrates a forming press 100 having a movable upper punch assembly 102 and a lower fixed base assembly 104. The upper punch assembly 102 is movable between a retracted position spaced from the fixed base assembly 104 and an extended position adjacent to the fixed base assembly 104 at a bottom dead center position of the forming press 100. The upper punch assembly 102 includes a punch piston 106 mounted in an upper die shoe 108, and the lower fixed base assembly 104 includes a lower die shoe 110.
A bead punch assembly 112 is secured in fixed relation to the upper die shoe 108 and includes an annular outer bead punch 112a, an annular middle bead punch (first intermediate bead punch) 112b, and an annular inner bead punch (second intermediate bead punch) 112c. Punch bead spacers 115 may be provided to enable positioning of the middle bead punch 112b and inner bead punch 112c relative to each other and relative to the outer bead punch 112a. Further, an additional bead punch spacer 117 may be provided above the outer bead punch 112a to enable positioning the outer, middle, and inner bead punches 112a, 112b, 112c relative to the upper die shoe 108. Alternatively, the bead punch assembly 112 may comprise the outer bead punch 112a, middle bead punch 112b, and inner bead punch 112c formed integrally, i.e., as a single unit, with the positions of the bead punches 112a, 112b, 112c fixed relative to each other.
The upper punch assembly 102 further includes an upper panel punch 114 that is secured to the punch piston 106 and supported for movement relative to the bead punch assembly 112. One or more spacers 119 may be provided between the punch piston 106 and the upper panel punch 114 to adjust the vertical position of the upper panel punch 114 within the upper die shoe 108. In the illustrated configuration, two spacers 119 of different diameter are illustrated wherein the thickness of one or both of the spacers 119 may be ground to adjust the vertical position of the upper panel punch 114. In an alternative configuration, a single spacer having a stepped diameter could be provided in place of the two spacers 119 illustrated herein. In the illustrated embodiment, the inner bead punch 112c may be located at the same height or slightly above the outer bead punch 112a, and the middle bead punch 112b may be located at a height above both the outer and inner bead punches 112a, 112c, see Fig. 3.
The lower fixed base assembly 104 includes a lower bead die assembly 116 for cooperating with the bead punch assembly 112 during a forming process performed on a workpiece or blank 130 which is cut from a sheet of material in the forming press. The bead die assembly 116 comprises an annular outer bead die 116a, an annular middle bead die 116b, and an annular inner bead die 116c. Additionally, the lower bead die assembly 116 includes a lower panel punch 118 for cooperating with the upper panel punch 114.
Die spacers 120 can be provided to position the middle bead die 116b and inner bead die 116c relative to each other and relative to the outer bead die 116a, and a lower panel punch spacer 122 can be provided to position the lower panel punch relative to the inner bead die 116c. Alternatively, the lower bead die assembly 116 may comprise the outer bead die 116a, middle bead die 116b, inner bead die 112c, and lower panel punch 118 formed integrally, i.e., as a single unit, with the positions of the bead dies 116a, 116b, 116c fixed relative to each other and fixed relative to the lower die assembly 116.
As seen in Fig. 1, an upper surface of the lower panel punch 118 is located at an elevation or height that is below the height of the inner bead die 116c. Further, in the illustrated embodiment, the middle bead die 116b may be located at a greater height than the inner bead die 116c, and the outer bead die 116a may be located at a greater height than the middle bead die 116b. It should be understood that the heights of the bead punches 112a, 112b, 112c and bead dies 116a, 116b, 116c relative to each other are selected to provide a sequential forming of beads for the can end that facilitate formation of the can end with no or limited stretching of the blank material, as will be described further below.
As shown in Fig. 1, the upper punch assembly 102 is moved from the retracted position toward the extended position, and is located adjacent to the fixed base assembly 104 to cut a can end blank 130 from the sheet or workpiece W. The can end blank 130 is cut from the sheet or workpiece W by a blank or draw punch 124 carried by the upper punch assembly 102, and a cut edge 126 carried by the fixed base assembly 104. An outer peripheral portion 130A of the can end blank 130 is clamped at an outer clamping area 128A between the draw punch 124 and a draw pad 128 movably supported on the fixed base assembly 104 of the forming press 100 so that the can end blank is held in a generally horizontal orientation as shown. A knockout ring 132 carried by the upper punch assembly 102 is engaged against a crown portion 130B of the blank 130 adjacent to the outer peripheral portion 130A, as can be further seen in Fig. 2.
Referring to Fig. 3, during downward movement of the upper punch assembly 102 toward the extended position, the knockout ring 132 moves into association with a crown ring 134 to clamp the crown portion 130B at a crown clamping area 134A between the knockout ring 132 and the crown ring 134. The draw pad 128 is supported in the fixed base assembly 104 on an air cushion.
Further downward movement of the draw punch 124 with the upper punch assembly 102, following clamping at the crown clamping area 134A, moves the outer clamping area 128A down below the crown clamping area 134A, such that the peripheral portion 130A is extracted from the outer clamping area 128A.
At substantially the same time or after the peripheral portion 130A is released from the outer clamping area 128A, the upper panel punch 114 can engage against the center panel portion 130. The crown ring 134 is rigidly supported in the lower fixed base assembly 104 and the knockout ring 132 is spring biased downwardly in the upper punch assembly 102. Hence, the knockout ring 132 can retract into the upper punch assembly 102 following clamping of the crown portion 130B in the crown clamping area 134A and as the upper punch assembly 102 continues to move toward the fixed base assembly 104. Further continued downward movement of the upper punch assembly 102 engages the upper panel punch 114 against a center panel section 131 of the blank 130 to the position shown in Fig. 3.
It may be noted that an air pressure is applied to a chamber 107 above the punch piston 106, see Fig. 1, during the downward stroke of upper punch assembly 102 to bias the upper panel punch 114 downwardly relative to the bead punch assembly 112 throughout the downward stroke of upper punch assembly 102. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.295 in. (0.749 cm) between the position shown in Fig. 2 and the position shown in Fig. 3. It may be understood that the particular dimensions identified with reference to movement of the tooling in the steps of the forming process described with reference to Figs. 2-9 are provided for exemplary purposes only, and are not intended to be limiting to the invention claimed herein. That is, the dimensions of tooling movement are provided to illustrate a relative degree of movement throughout the forming process, and variations in the particular movement or degree of movement of the tooling can be included within the forming process described herein.
Referring to Fig. 4, during further downward movement of the upper punch assembly 102 toward the extended position, the upper panel punch 114 is positioned to clamp the center panel portion 130C in a panel clamping area 118A between the upper panel punch 114 and the lower panel punch 118 to define a center panel valley portion 130C of the blank 130, which substantially corresponds to the center panel section 131. At generally the same time as the upper panel punch 114 moves into position to define the center panel valley portion 130C, the outer bead punch 112a engages the blank 130 adjacent to the crown clamping area 134A to partially form the crown portion 130B around the upper surface of the crown ring 134 and draw a portion 130A of the outer peripheral portion around the crown ring 134.
Additionally, as a lower surface of the upper panel punch 114 moves below the inner bead die 116c, a portion of the blank 130 adjacent to the center panel portion 130C is positioned in engagement over the inner bead die 116c. At this stage of the can end formation, an intermediate area 130D of the blank 130 spanning between the upper bead punch 112a and the inner bead die 116c comprises a substantially undeformed portion of the blank 130 that is out of engagement with the middle and inner bead punches 112b, 112c and out of engagement with the outer and middle bead dies 116a, 116b. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.067 in. (0.170 cm) between the position shown in Fig. 3 and the position shown in Fig. 4.
Referring to Fig. 5, during further downward movement of the upper punch assembly 102 toward the extended position, the center panel section 131 remains clamped in the panel clamping area 118A, and the outer bead punch 112a continues to press an outer periphery of the intermediate section 130D downward and draw additional material from the outer peripheral portion 130A of the blank 130 around the crown ring 134. As the bead punch assembly 112 moves downward, the upper panel punch 114 is displaced upward relative to the bead punch assembly 112, against the air pressure in the chamber 107. Additionally, the outer bead punch 112a can begin a deformation of the material of the blank 130 as an initial step in formation of an annular outer bead for the can end. It may be noted that as material is drawn from the outer peripheral portion 130A, it passes through a die area defined between an inner wall 125 of the draw punch 124 and an outer wall 135 of the crown ring 134 to form a generally vertical outer wall for the can end. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.010 in. (0.025 cm) between the position shown in Fig. 4 and the position shown in Fig. 5.
Referring to Fig. 6, during further downward movement of the upper punch assembly 102 toward the extended position, the center panel section 131 remains clamped in the panel clamping area 118A, and the outer bead punch 112a continues to press an outer periphery of the intermediate section 130D downward and draw additional material from the outer peripheral portion 130A of the blank 130 around the crown ring 134. As the bead punch assembly 112 moves downward, the upper panel punch 114 is displaced further upward relative to the bead punch assembly 112, against the air pressure in the chamber 107. The outer bead punch 112a moves the intermediate section 130D into contact or closely adjacent to contact with one or both of the outer and middle bead dies 116a, 116b, while the middle and inner bead punches 112b, 112c can remain out of contact with the intermediate section 130D. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.010 in. (0.025 cm) between the position shown in Fig. 5 and the position shown in Fig. 6.
Referring to Fig. 7, during further downward movement of the upper punch assembly 102 toward the extended position, the center panel section 131 remains clamped in the panel clamping area 118A, and the outer bead punch 112a continues to press the outer periphery of the intermediate section 130D downward and draw additional material from the outer peripheral portion 130A of the blank 130 around the crown ring 134. As the bead punch assembly 112 continues to move downward, the upper panel punch 114 is displaced further upward relative to the bead punch assembly 112, against the air pressure in the chamber 107. At the stage of formation shown in Fig. 7, the blank 130 can be in engagement with the first bead die 116a, and the outer bead punch 112a can press the material of the blank 130 into a first die space S₁ between the crown ring 134 and the outer bead die 116a, past or below the height of the outer bead die 116a, to form a countersink radius V₁, also referred to as a chuckwall radius. Further, the middle and inner bead punches 112b, 112c can remain out of contact with the intermediate section 130D as the countersink radius V₁ is formed. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.010 in. (0.025 cm) between the position shown in Fig. 6 and the position shown in Fig. 7.
Referring to Fig. 8, during further downward movement of the upper punch assembly 102 toward the extended position, the center panel section 131 remains clamped in the panel clamping area 118A, and the outer bead punch 112a continues to press the outer periphery of the intermediate section 130D downward and draw additional material from the outer peripheral portion 130A of the blank 130 around the crown ring 134. As the bead punch assembly 112 continues to move downward, the upper panel punch 114 is displaced further upward relative to the bead punch assembly 112, against the air pressure in the chamber 107. The middle bead punch 112b can press the material of the blank 130 into a second die space S₂ between the outer bead die 116a and the middle bead die 116b, past or below the height of the outer bead die 116a, to form a first intermediate or middle bead valley radius V₂, and further defining a first bead radius B₁ separating the first and second valley radii V₁, V₂. As the second bead valley radius V₂ is formed, the downward movement of the outer bead punch 112a with the bead punch assembly 112 continues to deepen the countersink radius V₁. It may be noted that material of the blank 130 may be drawn radially inward across the outer bead die 116a, the outer bead punch 112a, and the crown ring 134 with downward movement of the upper bead punch assembly 112 to provide material for forming the beads with little or no stretching of the material of the blank 130. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.010 in. (0.025 cm) between the position shown in Fig. 7 and the position shown in Fig. 8.
Referring to Fig. 9, during further downward movement of the upper punch assembly 102 toward the extended position, the center panel section 131 remains clamped in the panel clamping area 118A, and the outer bead punch 112a continues to press the outer periphery of the intermediate section 130D downward and draw additional material from the outer peripheral portion 130A of the blank 130 around the crown ring 134. As the bead punch assembly 112 continues to move downward, the upper panel punch 114 is displaced further upward relative to the bead punch assembly 112, against the air pressure in the chamber 107. The inner bead punch 112c can press the material of the blank 130 into a third die space S₃ between the middle bead die 116b and the inner bead die 116c, past or below the height of the middle bead die 116b and the inner bead die 116c, to form a second intermediate or inner bead valley radius V₃. Forming the inner bead valley radius V₃ further coincides with forming a second bead radius B₂ separating the middle and inner bead valley radii V₂, V₃ and forming or completing a third bead radius B₃ separating the inner bead valley radius V₃ and the center panel valley portion 130C. As the inner bead valley radius V₃ is formed, the downward movement of the outer and middle bead punches 112a, 112b with the bead punch assembly 112 continues to deepen the countersink radius V₁ and middle bead valley radius V₂. As noted above, the material of the blank 130 may be drawn radially inward as the upper punch assembly 102 moves downward. In particular, the material of the blank 130 may be drawn across the outer and middle bead dies 116a, 116b, the outer, middle and inner bead punches 112a, 112b, 112c, and the crown ring 134 with downward movement of the upper bead punch assembly 112 to provide material for forming the countersink radius V₁, and the middle and inner bead valley radii V₂, V₃ with little or no stretching of the material of the blank 130.
The forming stage illustrated in Fig. 9 represents downward movement at or close to the extended position of the upper punch assembly 102, and completes the outer peripheral portion 130A of the blank 130 to a final length defining an outer wall of a crown C of the can end. The crown C has a final contour defined by the upper surface of the crown ring 134 and is connected to the countersink radius V₁ at a vertical outer countersink wall 136 formed between an inner wall 138 of the crown ring 134 and an outer wall 140 of the outer bead punch 112a, as may be further seen in Fig. 10. In the illustrated exemplary embodiment, the upper punch assembly 102 may move downward about 0.031 in. (0.079 cm) between the position shown in Fig. 8 and the position shown in Fig. 9.
It should be understood that although the steps for forming a can end include initiating formation of the middle bead valley radius V₂ as a first intermediate bead valley radius following the step of initiating formation of the countersink radius V₁, additional aspects of the invention may include a different order of bead valley radius formation. For example, the bead punch assembly 112 and bead die assembly 116 may be configured to initiate formation of the inner bead valley radius V₃ as the first intermediate bead valley radius followed by initiating formation of the middle bead valley radius V₂ as the second intermediate bead valley radius.
From the above description, it may be understood that the can end is formed with successive formation of valley radii wherein initial formation of the valley radii may be staged to occur at different times in the forming process. In particular, formation of the countersink radius may be initiated first and successive intermediate valley radii may be formed sequentially which, in combination with only providing the upper forming tooling "on air" while the bottom tooling is "on solid" or fixed, results in a reduction in press tonnage required for formation of the can end.
In forming the can end, a bending of the material forming the blank 130 can be performed gradually wherein bending of the material can be accommodated by either pulling additional material from the outer portion 130A of the blank 130 or by a localized thinning of material at the bead radii or valley radii. Performing the forming operation as a sequential draping of the material over the tooling of the bead punch assembly 112 and bead die assembly 116, as is illustrated in Figs. 2-9, reduces restriction on movement of the material from the outer portion 130A, such that the material of the blank 130 is pulled inward more readily to reduce the amount of thinning that might otherwise occur. Hence, it may be understood that throughout the steps described with reference to Figs. 2-9, the material for forming the bead valley radii and bead radii, and in particular the material of the intermediate section 130D, is not substantially stretched but rather is formed with relatively small sequential deformations that thin the material a minimal amount to form the beads, while the center panel section 131 remains clamped at a stationary position. For example, the can end formation process described herein may be performed with no more than about 6% material thinning and no or negligible material stretching.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the scope of the invention, which is defined by the appended claims.

Claims

A method for forming a can end in a forming press (100), the method comprising:
positioning a sheet of material between an upper punch assembly (102) and a fixed base assembly (104) in the forming press (100);

cutting a can end blank (130) from the sheet of material;

clamping a peripheral portion (130A) of the can end blank (130); and

moving the upper punch assembly (102) from a retracted position toward an extended position, and clamping a central portion of the can end blank (130) between an upper panel punch (114) and a lower panel punch (118) to define a central panel section on the can end blank (130), wherein the central panel section is below an annular inner bead die (116c) located adjacent to the lower panel punch (118) on the fixed base assembly (104);

characterized in that the method comprises extending the upper punch assembly (102) subsequent to clamping the central portion of the can end blank (130) to form an initial annular countersink radius (V₁) next to the peripheral portion of the can end blank (130), with a substantially undeformed intermediate area (130D) extending between the initial annular countersink radius (V₁) and the annular inner bead die (116c).
The method of forming a can end as set forth in claim 1, including extending the upper punch assembly to engage an annular first intermediate bead punch (112b) against the can end blank and initially form a first intermediate bead valley radius (V₂) in the intermediate area (130D) of the can end blank, and simultaneously increasing the depth of the countersink radius (V₁).
The method of forming a can end as set forth in claim 2, including further extending the upper punch assembly to engage an annular second intermediate bead punch (112c) against the can end blank and initially form a second intermediate bead valley radius (V₃) in the intermediate area (130D) of the can end blank, wherein the depth of the first intermediate bead valley radius (V₂) and the countersink radius (V₁) is simultaneously increased.
The method of forming a can end as set forth in claim 1, wherein forming the initial annular countersink radius comprises engaging the can end blank with an outer bead punch (112a) on the upper punch assembly after an initial engagement of the upper panel punch against the can end blank.
The method of forming a can end as set forth in claim 4, wherein initial formation of the annular countersink radius (V₁) includes upward displacement of the upper panel punch (114) relative to the outer bead punch (112a) while the upper panel punch (114) clamps the central panel section to the lower panel punch (118).
The method of forming a can end as set forth in claim 4, wherein the peripheral portion (130A) of the can end blank is clamped on a crown ring (134) of the fixed base assembly, and the outer bead punch (112a) cooperates with an inner wall (138) of the crown ring (134) to form a generally vertical outer wall (136) of the countersink radius (V₁).
The method of forming a can end as set forth in claim 1, wherein the upper punch assembly (102) includes an annular outer bead punch (112a), an annular middle bead punch (112b), and an annular inner bead punch (112c), and the fixed base assembly (104) includes an annular outer bead die (116a), an annular middle bead die (116b), and the annular inner bead die (116c), and wherein, subsequent to an initial engagement of the outer bead punch (112a) on the can end blank:
the undeformed intermediate area (130D) of the can end blank extends in engagement with the outer bead die (116a), the middle bead die (116b) and the inner bead die (116c); and

the middle bead punch (112b) and the inner bead punch (112c) are located spaced from the can end blank.
The method of forming a can end as set forth in claim 7, wherein the middle bead punch (112b) engages the can end blank prior to an engagement of the inner bead punch (112c) on the can end blank.
The method of forming a can end as forth in claim 8, wherein the outer bead punch (112a) and the inner bead punch (112c) extend downward farther than the middle bead punch (112b).
The method of forming a can end as set forth in claim 9, wherein movement of the upper punch assembly to its extended position completes formation of the can end blank into a can end having a countersink radius (V₁), a middle bead valley radius (V₂), and an inner bead valley radius (V₃), wherein the central panel section remains clamped between the upper panel punch (114) and the lower panel punch (118) during the entire formation of the beads.
A method for forming a can end in a forming press (100), the method comprising:
positioning a sheet of material between an upper punch assembly (102) and a fixed base assembly (104) in the forming press;

cutting a can end blank (130) from the sheet of material;

clamping a peripheral portion (130A) of the can end blank (130) between a crown ring (134) and a knockout ring (132);

providing an upper punch assembly (102) having a plurality annular bead punches (112a, 112b, 112c) and an upper panel punch supported for movement relative to the bead punches (112a, 112b, 112c); and

providing a fixed base assembly (104) having a plurality of annular bead dies (116a, 116b, 116c) for cooperating with the bead punches (112a, 112b, 112c) and a lower panel punch (118), wherein the lower panel punch (118) is immovably fixed relative to the bead dies (116a, 116b, 116c);

characterized in that the method comprises moving the upper punch assembly (102) from a retracted position toward an extended position, wherein movement of the upper punch assembly (102) comprises:
engaging a central portion of the can end blank (130) with the upper panel punch (114) prior to engagement of the can end blank (130) with the bead punches (112a, 112b, 112c) or the bead dies (116a, 116b, 116c); and

subsequently moving the upper punch assembly (102) to clamp the central portion of the can end blank (130) between the upper panel punch (114) and the lower panel punch (118) with the can end blank (130) engaged with a single one of the bead punches (112a, 112b, 112c) and a single one of the bead dies (116a, 116b, 116c).
The method of forming a can end as set forth in claim 11, including extending the upper punch assembly (102) subsequent to clamping the central portion of the can end such that the single one of the bead punches (112a, 112b, 112c) moves the can end blank down into engagement with one or more of the remaining bead dies (116a, 116b, 116c).
The method of forming a can end as set forth in claim 12, wherein, subsequent to the can end blank moving into engagement with the one or more of the remaining bead dies (116a, 116b, 116c), further movement of the upper punch assembly (102) moves the remaining bead punches (112a, 112b, 112c) into engagement with the can end blank.
The method of forming a can end as set forth in claim 11, wherein the single one of the bead punches comprises a radially outermost bead punch (112a) and the single one of the bead dies comprises a radially innermost bead die (116c).
The method of forming a can end as set forth in claim 14, wherein a substantially undeformed intermediate area (130D) extends between the outermost bead punch (112a) and the innermost bead die (116c).
Apparatus for forming a can end from a sheet of material in a single acting press (100) having a fixed base assembly (104) and a movable upper punch assembly (102), the apparatus comprising:
a crown ring (134) rigidly supported on the fixed base assembly (104) and having an upper surface defining a contour for a crown (130B) of the can end;

a knockout ring (132) carried by the upper punch assembly (102), the knockout ring (132) being aligned with the crown ring (134) for engaging a workpiece (130) upon movement of the upper punch assembly (102) toward the fixed base assembly (104) to form a crown (130B) in a peripheral portion of the workpiece (130);

a plurality annular bead punches (112a, 112b, 112c) supported on the upper punch assembly (102) and an upper panel punch (114) fluidly supported on the upper punch assembly (102) for movement relative to the bead punches (112a, 112b, 112c);

a plurality of annular bead dies (116a, 116b, 116c) and a lower panel punch (118) supported on the fixed base assembly (104) for cooperating with the bead punches (112a, 112b, 112c) and the upper panel punch, respectively;

characterized in that the movement of the upper punch assembly (102) from a retracted position toward an extended position engages the workpiece (130) between the crown ring (134) and the knockout ring (132), and positions the upper panel punch (114) in engagement with the workpiece (130) prior to engagement of the workpiece (130) with the bead punches (112a, 112b, 112c) or the bead dies (116a, 116b, 116c), and subsequent movement of the upper punch assembly (102) clamps the workpiece (130) between the upper panel punch (114) and the lower panel punch (118) with the workpiece (130) engaged with a single one of the bead punches(112a, 112b, 112c) and a single one of the bead dies (116a, 116b, 116c).
The apparatus for forming a can end from a sheet of material in a single acting press as set forth in claim 16, wherein the upper panel punch (114) displaces into the upper punch assembly (102) during movement of the punch assembly toward the extended position subsequent to clamping the workpiece (130) between the upper panel punch (114) and the lower panel punch (118).
The apparatus for forming a can end from a sheet of material in a single acting press as set forth in claim 17, wherein the plurality of bead punches (112a, 112b, 112c) on the upper punch assembly are supported in fixed relation to each other and the upper panel punch (114) is movable relative to the plurality of bead punches (112a, 112b, 112c).